SHP-1 limits natural intestinal Th17 development. (A) IL-17 expression of CD4⁺ gated T-cell population isolated from the Peyer patches of +/+, me/+, and me/me BALB/c DO11.10 and C57BL/6 mice. +/+ and me/+ mice have comparable numbers of CD4⁺ cells, whereas me/me mice have 50% reduced CD4⁺ cell numbers in their Peyer patches correlating with their decreased size (data not shown). (B) Representative colon segments from +/+ (n = 8), me/+ (n = 7), and me/me (n = 8) BALB/c DO11.10 mice (H&E, original magnification ×200). (C-D) Percentages of IL-17A/F⁺ cells within the CD4⁺ compartment isolated from the Peyer patches (C) and intestinal lamina propria (D) of mice with the indicated genotypes. (E) IL-17 expression of CD4⁺ gated T-cell population isolated from inguinal lymph nodes, mesenteric lymph nodes, and spleen of +/+, me/+, and me/me C57BL/6 and BALB/c DO11.10 mice. Data are representative of 2 to 4 independent experiments with multiple mice for each genotype per experiment.